Method of making belts



Oct. 30, 1951 J. A. HURRY METHOD OF MAKING BELTS Filed Aug. 2, 1947 FLUID PRESSURE RESERVOIR V// x! fig WALL 0F VULCANiZING KETTLE 6' 9 ZI 2 I In I 6, ga 12 21 9 I my n 23 ,4 74 Z3 I I I I I i ,2;

IN V EN TOR. JAMS' A. HURR Y.

Patented Oct. 30, 951

METHOD OF MAKING BELTS James A. Hurry, Denver, 0010,, assignor to Gates Rubber Company, Denver, 0010., a corporation of Colorado Application August 2, 1947-, Serial No. 765,738

ZClaims'. I 1

This invention relates to improvements in methods for manufacturing and curing power transmission belts.

The transmission of power between different machines is today effected quite generally by means of power transmission belts of the V-type which have been and are rapidly replacing gear and sprocket chain transmissions.

Belts of this type, especially such as are used between comparatively short centers are nearly always moulded in endless form. There are in use today several methods of manufacturing belts of this general type, which however, will not be described here.

Power transmission belts are practically all provided with an endless tension core usually formed from fabric cords such as cotton, rayon or nylon and which are also at times formed from stranded metal cables. 7

In the manufacture of power transmission belts of the type mentioned above, it is quite essential that the tension core shall be kept under a comparatively high tensional strain during the curing of the belt. This assures that the belt will not increase unduly in length after it has been put into operation. o

' In belts of the V-type, the tension layer is usually positioned much closer to the outside or wide surface of the belt than to the inner and narrow side, and the body of the belt between the tension layer and the narrow side is nearly always composed of material formed entirely or in part, by rubber composition. Where belts of' this type are cured in the ordinary way, the tension layer is not subjected to any substantial amount of tensional strain during the curing operation with the result that the belt has a tend-t ency to increase in length afterit has been in use for some time.

It has also been found that if belts of the V -type, cured with the wide surface towards the outside, are subjected to tension during the curing, such tension has a tendency to move the tension layer inwardly at opposed points lnthe belt, leaving the tension layer in an unsymmetri construction. This method involves the idea of; the belt with the wide surfacejnnermostg 2 or, as may be designated briefly, in inverted position.

In the manufacture of power transmission belts of the type to which this invention relates, it is desirable that the cords or cables forming the tension layer shall be under uniform strain throughout their entire length during the curing operation and this invention relates more particularly to a method of making and curing belts of this type in such a manner that the tension layer will be maintained under uniform strain throughout its entire length during the curing operation.

This invention, briefly described, consists in curing V-type belts in an inverted position, that is, with the'narrow side towards the outside, and subjecting the belt to an expanding force applied to its wider surface in such a manner as to force the belt outwardly into a groove mould and to maintain the tension layer under strain during the curing operation.

Having thus briefly described the objects of the invention and, in a general way, the method employed, the invention will now be described in detail and for this purpose reference will be had to the accompanying drawing in which;

' Figure l is a diametrical section through a mould designed for use in carrying out this method, taken on line l-I, Figure 2;

Figure 2 is a bottom plan view of the mould partly broken away; and

Figure 3 is a fragmentary section, like that shown in Figure 1, shown to an enlarged scale.

The method. to which this invention relates is carried out by means of a mould which will now be described and which consists of two end closure plates 5 and 6, which are preferably circular as shown in Figure 2. The end closure plates are formed from metal such as steel and are quite massive so as to resist heavy strains. The end closure plates are provided with central openings 1 for the reception of a bolt 8 that secures them in assembled position, one end of the bolt having an opening for the reception of the wedge 9. The two end closure plates are substantially identical, the only difference in those shown is that the bottom closure is provided with three or more downwardly extending lugs I0 that serve to space the same from the bottom of the vulcanizing kettle. Such lugs may also be present in the top end closure, if desired. The closure plates are also provided with a number of openings like those designated by reference numeral ll. Each closure plate is provided with an annular recess or groove, whose bottom The outer diameter of rings l6 are somewhat I greater than the outer diameter of cylinder 15 for a purpose which will hereinafter appearfi Rings [6 are positioned in annular grooves or channels I9 in rings 20, the latter fitting into grooves l2, as shown in the drawing. Rings 20 are secured to rings l6 by means of bolts 2|. heavy rubber cylinder ZZsurrounds the assembly comprising cylinder l and rings I6. The walls oficylinder 22 are somewhat reduced in thickness near their ends and project into the grooves in rings 20 and are positioned between-the outer wall 23 of rings20 and the outer surface of rings I 6. Theends of cy1inder'22 are then bent inwardly so as to lie between theends of rings l6 and the bottom of groove 19 andareclamped in position by bolts 2|. Sincethe outer-diameter of ring it is slightly greater than the outside diameter of cylinder l5, a narrow space 24 is formed between the metal cylinder and the rubber cylinder. Metal cylinder 15 is provided with a hole 25 for the reception of one end of an air hose 26 which extends to a reservoir containing air under pressure. -Between the flanges l3 of the end closures 5 and 6, there are positioned several rings. Those nearest the ends have been designated by reference numeral 21, 21a and the intermediate rings byv reference numeral 28. There may be as many of the intermediate rings as desired, as shown in Fig. '2, butin Figure l only one ring 28 has-been shown complete. and theothers have been shown in broken form. i

It, will be observed that rings 27, 27a are provided near their endswith a .rabbet .29; into which the flanges 13 extend. The other edge of the uppermost ring 21 is provided with a tongue 30 and has an inclined wall 3| that is connected with the tongue bymeans, of afiat surface 32. The lowermost ring 27a is provided with an annular groove 33 instead of with a tongue 30 like that of the upper ring. The lowermost ring 21a is provided with an inclined wall 3| con-j nected with the groove 33 by means of a flat surface 34. Rings 28 are of the shape shown in the drawing and are provided on their upper surfaces with grooves 35 for the reception of the tongues 30, their inner surfaces having inclined walls am that cooperate with walls 3| to form a groove of the size and shape of the belt to be cured therein.

The belts to be cured in this form are first built up in the usual manner and cut to substantially the size and shape desired. The form shown in the drawing is positioned on a support-, ing surface like that one designated by refer-- ence numeral 35 and the lowermost ring 210, rests on the bottom end closure. A beltis then= positioned against the inclined surface 3la of ring 27a. This belt has been indicated by cross hatching and designated by reference numeral 37. A ring 28 is now positioned on the upper edge of the lowermost ring 2111. and another belt is positioned against the inclined surface am.- This is continued until all of the grooves are 5 sembled position. Fluid under pressure, either air, steam or water, is now supplied to space 24 from a suitable source. The pressure thus introduced will-force the belts outwardly against the inclined Walls of the mould and because cylinder The weld, 22 is made of elastic material and forced outwardly by fluid pressure, it will exert equal radial forces along all points. Increasing the diameter of the belt by means of this uniform radial pressure subjects the tension cords to a uniform tensional strain. The assembly is now positioned in a vulcanizing kettle and subjected .=to heat provided by'steam of the proper temperature. The steam not only surrounds the outside of the form, but also fills the interior because the end closures are provided with openings H, as

already pointed out. The pressure supplied to chamber 24 must be'greater than the pressure of the steam employed in the curing because the effective pressure is the difference between the pressure of the expanding fluid and that of th steam used for heating.

- After the belts have been cured, the mould is removed from thevulcanizing kettle and opened; the belts are then removed and the mould filled with uncured belts andthe operation repeated.

- Attention is again directed to the very important feature, namely, that by the above described means the tension layers in the belts are stretched uniformly along their entire lengths,

thereby assuring'that the belt will have the same characteristics at all transverse sections and assuring further, that the belt will substantially retain its original length when put into use.

In the drawing the mould has been shown as designed for the curing of belts of the V-type.

It is to'be understood that belts of any other cross sectional shape may be cured in the same way. v I

j Attention is called to the fact that in this mould and'with this method the belts are cured with their narrow wall towards the outside;

Such belts must be reversed for use with V-typev pulleys producing thereby belts having some physical characteristics not found in belts of the V-type cured with the narrow side inside.

7 The material of the body of the belt is usually rubber composition such as ordinarily employed, but may be'made'of any one of'the so-called synthetic rubbers, plastics or fabrics. The tension layer is usually formed from cotton cords, but may be of rayon or nylon Orally other suit-jable material.

Having described the invention what claimed as new is:

l. The 'method' of forming an endless power transmission V-belt, the body of which comprises a heat curable material having an endless tension core therein consisting of substantially parallel cords, which includes the steps of positioning the belt in an endless outwardly narrow-- ing mould cavity, said cavity being of a size to enable at least a portion of the belt to move points therealong, and subjecting the belt to a curing temperature while maintaining said core tensionally strained.

2. The method of forming an endless power transmission belt, the body of which comprises a heat curable material having an endless tension core therein consisting of substantially parallel cords, which includes the steps of positioning the belt in an endless mould cavity or the desired shape of a finished belt, the open side of 10 the cavity facing inwardly and being of a size to enable at least a portion of the belt to move outwardly to increase the length thereof, forcing an endless wall of expansible material in an outward direction normal to and against the entire therealong, and subjecting the belt to a curing temperature while maintaining said core tensionally strained.

JAMES A. HURRY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,420,727 Moon June 27, 1922 1,432,973 Delzell Oct. 24, 1922 1,644,327 Dykes Oct. 4, 1927 2,253,792 Leavenworth Aug. 26, 1941' 2,292,290 Robins Aug. 4, 1942 2,324,991 Groncy July 20, 1943 2,327,566 Slusher Aug. 24, 1943 2,362,659 Miller Nov. 14, 1944 2,420,278 Yelm May 6, 1947 

